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Today's Goal: Today students will be able to estimate quotients (division problems) involving decimals using compatible numbers.
When estimating any quotient it is best to use compatible numbers. Compatible numbers are number that get along, they are in the same fact family, one is a multiple of the other. Let's look at a couple examples.
In the first example we will use a single digit divisor.
34.96 ÷ 6
We can't round the single digit number so we will have to round the 34.96. If we round to the greatest place value we get 35 and 35 is not a multiple of 6. Let's think of the multiples of 6. They are 6, 12, 18, 24, 30, 36, 42. Which of the multiples is closest to 35? The answer is 36 so that is what we will round 34.96 to. Our problem is now:
36 ÷ 6 so the quotient is 6.
What is we have a multi-digit divisor? Here is an example.
37.8 ÷ 4.7
First, round the divisor to a whole number. 4.7 rounds to 5
37.8 ÷ 5
Now think of the multiples of 5. 5, 10, 15, 20, 25, 30, 35, 40.
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